History

For centuries, people with Down syndrome have been referenced in art, literature and science. In 1866, John Langdon Down, an English physician, published the first accurate description of a person with Down syndrome. Because of this work, Down is considered the “father” of the syndrome. Although other people had previously recognized the characteristics of the syndrome, it was Down who described the condition as a distinct and separate entity.

In 1959, the French physician Jérôme Lejeune identified Down syndrome as a chromosomal condition. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome. It was later known that an extra partial or whole copy of chromosome 21 results in the characteristics associated with Down syndrome.

In the year 2000, an international team of scientists successfully identified and catalogued each of the approximately 329 genes on chromosome 21. This accomplishment has since opened the door to great advances in Down syndrome research.

 

Causes

The cause of Down syndrome is currently unknown, but research has shown that it increases in frequency as a woman ages.  But because of higher birth rates in younger women, 80% of children with Down syndrome are born to women under 35 years of age.  There is no definitive scientific research suggesting that Down syndrome is caused by environmental factors or the parents' activities before or during pregnancy.

The additional partial or full copy of the 21st chromosome which causes Down syndrome can originate from either the father or the mother. Approximately 5% of the cases have been traced to the father.